Esters of 4,4-ditert butylperoxypentanoic acid



United States Patent 3,433,825 ESTERS 0F 4,4-DITERT.BUTYLPEROXY-PENTANOI'C A'CID Pieter R. A. Maltha and Stephanus B. Tijssen,Schalkhaar,

Netherlands, assignors to Koninklijke Industrieele Maatschappij vorheenNoury and van der Lande N.V., Deventer, Netherlands, a corporation ofthe Netherlands No Drawing. Filed Oct. 10, 1963, Ser. No. 315,344

Claims priority, application Netherlands, Oct. 12, 1962,

284,315 US. Cl. 260-478 7 Claims Int. Cl. C07c 73/00, 69/66 ABSTRACT OFTHE DISCLOSURE The present invention relates to the production ofcopolymers and is particularly concerned with a process forcross-linking copolymers of ethylene and monomers containing CH =CHgroups with the aid of hitherto unknown peroxidic cross-linkinginitiators. The invention also relates to a process for preparing thesenew peroxides, as well as to the new peroxides per se.

In the cross-linking of copolymers of ethylene and monomers containingCH =CH groups, such as oopolymers of (1) ethylene and propylene and of(2) ethylene and vinyl acetate, etc., use is often made ofdicnmylperoxide as an initiator. However, the use of this peroxide as aninitiator has the disadvantage that the finished products obtained byits use possess a disagreeable odor. As a consequence, peroxidicinitiators such as this cannot be used in many instances.

It has been found, surprisingly, that hitherto unknown peroxides of thegeneral formula in which R is a hydrocarbon group having at most carbonatoms, are very suitable initiators in the cross-linking of copolymersof ethylene and monomers containing CH =CH-- groups, because theseperoxides do not give a disagreeable odor to the finished cross-linkedproducts and are almost equal in eflectiveness to the peroxide mostsuited to this purpose, namely, dicumylperoxide, so far as their otherproperties are concerned.

The cross-linking of copolymers of ethylene with the aid of the novelperoxidic initiators according to the present invention may be carriedout in the usual apparatus under otherwise conventional conditions oftemperature and pressure, and if desired, in the presence ofconventional auxiliary agents such as carbon black, sulphur orsulphur-releasing compounds such as tetramethyland 3,433,825 PatentedMar. 18, 1969 tetraethylthiuramdisulphide, and accelerators such asdiphenylguanidine.

The peroxides to be used according to the present invention may beobtained by reacting tert.butylhydroperoxide, at a temperature of 20 -35C., with an alkyl, aryl, aralkyl, or cycloalkyl ester of 3-ketobutanecarboxylic acid in stoichiometric proportions, in the presence of anacid-reacting catalyst, and preferably a mineral acid such as a solutionof 70% by weight of sulphuric acid in water, and eliminating the waterformed during the reaction, plus any water that might be present in thestarting material, plus the water in the sulphuric acid solution, bydistillation with the aid of an added entrainer, or a suitabledehydrating agent, which may preferably be anhydrous oxalic acid. In thelatter case, this organic acid surprisingly acts simultaneously as acatalyst so that when present at the beginning, the use of the mineralacid is superfluous (as shown below in Example 3).

The alkyl esters of 3-ketobutane carboxylic acid include both straightand branched chain alkyl-esters, especially the n-butyl ester and the2-ethylhexyl ester; the aryl esters including especially the phenylester; the aralkyl esters including especially the benzyl ester; and thecycloal-kyl esters including especially the cyclohexyl ester.

In order that the present invention in all its ramifications may bestill more readily understood, the following specific examples aregiven. Where in these examples reference is made to compression, thiswas determined with the aid of the Williams plastimeter in the same wayas described in S.P.E. Journal, 17 (1961), 265-270, but with the addedproviso that instead of a weight of 10 kg. a weight of 5 kg. was used.

EXAMPLE 1 34.4 g. (0.2 mole) of 3-ketobutanecarboxylic acid nbutyl esterwere mixed with stirring, in a 3-neck flask of 500 m1. capacity providedwith a mechanical stirrer, thermometer and water separator, with 36 g.(0.4 mole) of 100% tert.butylhydroperoxide and with 150 ml. of benzeneas an entrainer. Thereafter, also with stirring within 1 minute 0.2 ml.of sulphuric acid (70%) was added dropwise, care being taken that thetemperature of the reaction mixture was maintained at 2530 C. The waterof reaction, as well as the water present in the starting material, wasdistilled off azeotropically under reduced pressure during the reaction.After separation of the water in the water separator, the benzene wasrecycled to the three-neck flask.

After the reaction, the reaction mixture was freed from acid by washingsubsequently twice with 100 ml. of water, twice with 100 ml. of 2 NNaOH, and finally once again with 100 ml. of water.

After drying over sodium sulphate, the benzene was distilled off underreduced pressure at a final pot temperature of a maximum of 40 C.

68.3 g. of 3,3-ditert.butylperoxybutanecarboxylic acid n-butyl esterwere obtained, as follows:

Yield percent 93 Peroxide content do 91 Active oxygen content do 8.72

EXAMPLE 2 73.6 g. (0.2 mole) of 3-ketobutanecarboxylic acid stearylester were mixed with stirring, in a 3-neck flask of 500 ml. capacityprovided with a mechanical stirrer, thermometer and water separator,with 48.0 g. (0.4 mole) of tert.butylhydroperoxide and with ml. ofditert.butylperoxide as a carrier. Thereafter, 0.1 ml. of sulphuric acid(70%) was added dropwise with stirring 3 4 within 1 minute, care beingtaken that the temperature of as follows: the reaction mixture wasmaintained at 2530 C. The Peroxide content "percent" 81 water ofreaction, as well as the water present in the start- Active oxygencontent 8A7 ing material, Was eliminated from the reaction mixture "20L4282 during the reaction by distilling under reduced pressure 5 withthe aid of the ditertbutylperoxide. After separation n buty1 ester wereObtained in an analogous Way, Starting of the water in the waterseparator, the ditert.butylperfrom 344 (02 mole) of 3ketobutanecarboxylic acid oxide was recycled to the 3-neck flask. Thereaction mixmbuty} ester, as f l ture thus obtained was freed from acidin the same man- 46.0 g. of 3.3-ditert.butylperoxybutanecarboxylic acidPeroxide content percent 83 net as described m Example Active oxygencontent do 7.95 After drying over sodium sulphate, the carrier was n1.4306

eliminated by distillation under reduced pressure at a with the variousproducts thus obtained, mixtures com final P P Of miXimllm 0f 104 15taining the following parts by weight were made up on of 3,3ditert.butylperoxybutanecarboxylic acid stearyl a mixing roll at atemperature of 85 C.:

A. B C D E F G H J' K L M N Copolymer of ethylene and propylenecontaining 50% by weight of ethylene 100 100 100 100 100 100 100 100Copolymer of ethylene and vinylacetate containing by weight ofvinylacetate--. 100 100 100 100 100 HAF carbon black 50 50 50 50 50 5050 50 50 50 50 50 Dicumylperoxide 2, 7 2.7

Ester of 3,3-di(tert.butyl peroxy) butane carboxylic acid:

E hyl 1. 53

p Diphenylguanidine Triallylcyanurate-. 2 2 2 2 2 ester was obtained, asfollows: 35 The mixtures thus obtained were cross-linked by work- YieldPercent 87 ing in a press at 165 C. for a period of 40 minutes. AfterPeroxide. content 88 30 minutes at a temperature of 120 C., thecompression Active oxygen content 5 33 of samples from sheets thusobtained were de erm ed- Melting point after recrystallisation frommeth- The results were as follows:

anol C 3 638 40 The following peroxides were obtained in an analogousway: 3,3-ditert.butylperoxybutanecarboxylic acid ethyl, sheet z ggi igSheet Z-ethylhexyl, cyclohexyl and benzylester, respectively.

62 e 4 9 11 3 a 10 5 7 4 Ester of 3,3-di- Active 0- Peroxide 5 5 tertbutylcontent content n20 Yield 4 peroxybutane in percent in percent inpercent carboxylic acid: Ethyl 9.33 90 1.4289 32 50 3g 3%? 5 With theexception of sheets B and J, the sheets did BanzyLl 84 114746 80 notpossess a disagreeable odor.

While specific examples of preferred methods embodying the presentinvention have been set forth above, it will be understood that manychanges and modifications EXAMPLE 3 may be made in the methods ofprocedure without de- In a 3 neck flask of 500 mL capacity provided witha parting from the spirit of the invention. It will therefore mechanicalstirrer, thermometer and reflux condenser, be undqrstood that theexamples cltefi and i g 19.8 g. (0.22 mole) of anhydrous oxalic acidwere added Propomons and methods of operauon set on a ove by Smallincrements with Stirring to a mixture of 28 8 g are intended to beillustrative only, and are not intended (0.2 mole) of3-ketobutanecarboxylic acid ethylester and gg i i 1?: f mventlon' 3.6 g.(0.4 mole) of 100% tert.butylhydroperoxide, care a 1 an e being takenthat the temperature of the reaction mixture An organic peroxlde havmgthe general formula did not exceed 30 C. The mixture obtained was heatedfor 3 hours at 30 C. and subsequently cooled, with stirring, to roomtemperature. Subsequently the solid ma- (01191 terial present in thereaction mixture was filtered off. The remaining clear solution was,after having been diluted H with 100 m1. of benzene, freed from acid inthe same way 2 as described in Example 1. After drying over sodiumsulphate, the benzene was R distilled oif under reduced pressure at afinal pot temperature of not more than 40 C. 37.2 g. of3,3-ditert.butylin which R is a hydrocarbon group having not more thanperoxybutanecarboxylic acid ethyl ester were obtained, 20 carbon atoms-5 6 2. Ethyl ester of 4,4-ditert.butylperoxypentanoic acid. ReferencesCited 3. n-Butyl ester of 4,4-ditert.butylperoxypentanoic acid. UNITEDSTATES PATENTS 4. Stearyl ester of 4,4-ditert.butylperoxypentanoic acid.2 455 569 12/1948 k 260 610 5. Z-ethylhexyl ester of4,4-ditert.butylperoxypentanoic 1c ey acid. 5 LORRAINE A. WEINBERGER,Primary Examiner.

6. Benzyl ester of 4,4-ditert.butylperoxypentanoic acid. BERGER,Assistant 7. Cyclohexyl ester of 4,4-ditertbutylperoxypentanoic U S C1XR acid. 26088.2, 479

Notice of Adverse Decision in Interference In Interference No. 100,305,involving Patent No. 3,433,825, P. R. A. Maltha and S. B. Tijssen,ESTERS OF 4,4-DIETERT. BUTYLPEROXYPENTANOIC ACID, final judgment adverseto the patentees was rendered Feb. 10, 1981, as to claim 1.

[Official Gazette June 2, 1981.]

